William Bryan was born about 1760. He passed away in either Oct or Nov 1821.
The date of birth was estimated by examining the 1800, 1810 and 1820 census in Johnston County for William Bryan. Based on those three census and assuming the information regarding given age range was correct, William Bryan would have been born between 1756 and 1765. The date of birth was refined using the tax rolls. The Tax law according to an article by Raymond A. Winslow, Jr. in the book North Carolina Research edited by Helen F. M. Leary and Maurice R. Stirewalt and published by the North Carolina Genealogical Society, 1980, states that "in 1784 the colonial method of reckoning was restored somewhat and the legislature decreed that "freemen and male servants twenty-one years old and upwards, and slaves male and female between the age of twelve and fifty years, shall be subject to a poll-tax"". On the 1810 tax list in Johnston County William Bryan was indicated to have one free poll. On the 1811 tax list he was indicated to have no free polls. Thus one could assume he became exempt in the year 1811 which would place his birth date in 1761 fifty years earlier. I chose to use 1760 because experience with tax lists has shown that occasionally a year delay in claiming an exemption is not uncommon.
The date of death was estimated based on the Will of William Bryan which he signed on 7 Oct 1821 and it was exhibited for probate on 27 Nov 1821. There for he most likely died either in October or November of 1821.
Note: An SAR application had an exact death date of 14 Oct 1821 but I have not found a record to verify that date.
It may be possible to confirm family relationships with William by comparing test results with other carriers of his Y-chromosome or his mother's mitochondrial DNA.
Y-chromosome DNA test-takers in his direct paternal line on WikiTree: